The prodromal phase of glaucoma is characterized by transient or recurrent attacks, often occurring multiple times, typically in the evenings. During an attack, patients suddenly experience blurred vision and halos around lights, possibly accompanied by pain in the forehead on the affected side or a sour swelling at the root of the nose on the same side. These symptoms are short-lived and can resolve or disappear after rest. If examined immediately, increased intraocular pressure can be detected, often above 40 mmHg, with slight conjunctival congestion or no congestion. There is mild foggy edema in the corneal epithelium. The anterior chamber is extremely shallow, but the aqueous humor is clear, with a wide closure of the chamber angle, slightly dilated pupils, and sluggish light reflexes. After a minor attack subsides, aside from the characteristic shallow anterior chamber, there generally is no permanent tissue damage.